Pesticidal pyrimidine compounds

ABSTRACT

Compounds of formula (I) in which X 1  and X 2  each represents oxygen; S(O) n , n being 0, 1 or 2; or CO, CH 2  or NR, R being hydrogen or alkyl; R 1  and R 10  are each hydrogen or halogen; R 2  and R 9  are each hydrogen, halogen, cyano, nitro, alkyl, halo-alkyl, alkoxy, alkylthio, amino, mono- or di-alkylamino, alkoxyalkyl, haloalkoxyalkyl or alkoxycarbonyl; R 3  and R 8  are each hydrogen, chlorine, alkyl, haloalkyl, haloalkenyl, halo-alkynyl, haloalkoxy, haloalkoxycarbenyl, haloalkylthio, haloalkoxyalkyl, haloalkylsulphinyl, or haloalkylsulphonyl, nitro or cyano; R 4  and R 7  are each hydrogen, halogen, alkyl or alkoxy; R 5  is hydrogen, halogen, cyano, alkyl, haloalkyl, alkoxy, alkylthio, alkylsulphonyl or phenyl; and R 6  is hydrogen or, when R 5  is hydrogen, alkyl; provided that either each phenyl is unsubstituted or at least one of R 3  and R 8  is not hydrogen, have useful pesticidal activity.

This is a section 371 application of PCT/EP93/01880, filed Jul. 15,1993.

The present invention relates to substituted pyrimidine compounds, theirpreparation and use as pesticides.

Dutch Patent Specification No. 6814057 discloses a wide range ofsubstituted pyrimidines and their use as fungicides.

J. Indian Chem. Soc., 52(8), 1975, 774-775, and 53(9), 1976, 913-914discloses a number of 2-amino-4,6-bis aryloxy and arylimino pyrimidinesand suggests that they may have useful biological properties.

It has now been found that a group of substituted pyrimidinesgenerically described in NL-6814057 but not specifically disclosedtherein have acaricidal activity which is significantly greater thanthat of 2-amino-substituted analogues.

The present invention provides a compound of the general formula##STR2## in which X¹ and X² are the same and each represents an oxygenatom; a group S(O)_(n) in which n is 0, 1 or 2; or a group CO, CH₂ or NRin which R represents a hydrogen atom or an alkyl group;

R¹ and R¹⁰ are the same or different and each represents a hydrogen atomor a halogen atom;

R² and R⁹ are the same or different and each represents a hydrogen atom,a halogen atom or a cyano, nitro, alkyl, haloalkyl, alkoxy, alkylthio,amino, mono- or di-alkylamino, alkoxyalkyl, haloalkoxyalkyl oralkoxycarbonyl group;

R³ and R⁸ are the same or different and each represents a hydrogen atom,a chlorine atom, or an alkyl, haloalkyl, haloalkenyl, haloalkynyl,haloalkoxy, haloalkoxycarbonyl, haloalkylthio, haloalkoxyalkyl,haloalkylsulphinyl, haloalkylsulphonyl, nitro or cyano group;

R⁴ and R⁷ are the same or different and each represents a hydrogen atom,a halogen atom or an alkyl or alkoxy group;

R⁵ represents a hydrogen atom, a halogen atom, or a cyano, alkyl,haloalkyl, alkoxy, alkylthio, alkylsulphinyl or phenyl group; and

R⁶ represents a hydrogen atom or, when R⁵ is hydrogen, an alkyl group;

provided that either each of the two phenyl rings is unsubstituted or atleast one of R³ and R⁸ is other than hydrogen.

To maintain activity the phenyl rings of formula I must be eitherunsubstituted or at least one must be 3-substituted.

An alkyl group, unless otherwise specified, is suitably a straight chainor branched chain group containing up to 12 carbon atoms, for example upto 8 carbon atoms. Preferably an alkyl group contains up to 6 carbonatoms. Especially preferred alkyl groups are methyl, ethyl and butyl.Any alkyl moiety which forms part of another group, for example thealkyl of a haloalkyl group or each alkyl of an alkoxyalkyl group,suitably has up to 6 carbon atoms, preferably up to 4 carbon atoms.Preferred alkyl moieties are methyl and ethyl.

Halogen is fluorine, chlorine, bromine or iodine. Haloalkyl andhaloalkoxy are especially trifluoromethyl, pentafluoroethyl, andtrifluoromethoxy.

Preferably each of X¹ and X² represents an oxygen atom, a sulphur atomor an NH group; especially each of X¹ and X² represents an oxygen atom.

R¹ and R¹⁰ are preferably the same and each represents a hydrogen orfluorine atom, especially a hydrogen atom.

R² and R⁹ are preferably the same or different and each represents ahydrogen atom, a halogen atom, especially fluorine, chlorine or bromine,a nitro, alkyl or cyano group.

R³ and R⁸ are preferably the same or different, each representing ahydrogen, fluorine or chlorine atom, or a nitro, C₁₋₄ alkyl, haloC₁₋₄alkyl, halo-C₁₋₄ alkoxy, haloC₂₋₄ alkenyl or (C₁₋₄ alkoxy)carbonylgroup. In especially preferred compounds each of R³ and R⁸ represents ahydrogen or chlorine atom or a trifluoromethyl, trifluoromethoxy,pentafluoroethyl or difluoroethenyl group or one of R³ and R⁸ representsa trifluoromethyl group and the other represents a hydrogen, chlorine orfluorine atom or a methyl, butyl, nitro, cyano or methoxycarbonyl group.

R⁴ and R⁷ are preferably the same or different and each represents ahydrogen or halogen atom or a C₁₋₄ alkyl group.

The pyrimidine ring, apart from the substituents at the 4- and the6-positions, may carry one other substituent. R⁵, in the 2-position,preferably represents a hydrogen or halogen atom or a halo C₁₋₄ alkyl,C₁₋₄ alkylthio, C₁₋₄ alkylsulphinyl or phenyl group, especially ahydrogen, fluorine, chlorine or bromine atom or a methylthio orethylthio group. R⁶, in the 5-position, preferably represents a hydrogenatom or, when R⁵ is hydrogen, a methyl group; R⁶ is, however, especiallyhydrogen.

The compounds of formula I may be prepared by appropriate adaptation ofconventional methods for obtaining disubstituted pyrimidines.

Conveniently, the compounds of formula I may be prepared by couplingappropriately substituted phenol(s), thiophenol(s) or aniline(s) and4,6-dihalopyrimidines in basic conditions, optionally using a solvent,at ambient or, if necessary, at elevated temperatures, for example inthe range of from 50° to 150° C. Desirably the reaction is carried outunder nitrogen. Such procedures are well known and are described in, forexample, J. Indian Chem. Soc. 52(8), 1975, 774-775, and 53(9), 1976,913-914.

Naturally for the preparation of symmetrically substituted pyrimidinecompounds of formula I, the reaction can be carried out in one step byusing a molar ratio of pyrimidine to phenyl compound of at least 1:2.For unsymmetrical compounds, separate introduction of the two arylsubstituents is required by a two-stage process.

The basic conditions may be provided using an alkali metal salt,conveniently a sodium or potassium salt, e.g. an alkali metal hydride orcarbonate, such as sodium hydride or potassium carbonate or otherconventional bases such as n-butyllithium. The solvent, if used, may beany polar organic solvent and must be selected to be compatible with thebase utilised in the reaction. Thus with potassium carbonate,dimethylformamide or dimethylsulphoxide are both suitable, and withsodium hydride, tetrahydrofuran may be used.

It is also possible to generate a 2-substituted 4,6-disubstitutedpyrimidine from a corresponding compound with a different 2-substitutionby standard procedures. Thus, for example, a 2-halo-4,6-disubstitutedpyrimidine may be prepared from a corresponding 2-amino compound usingan alkyl nitrite, for example tert-butylnitrite, and a suitable solvent,such as carbon tetrachloride; also a 2-hydroxy-4,6-disubstitutedpyrimidine may be converted into a 2-halo-analogue under the action of aphosphoryl halide, for example phosphoryl chloride or phosphorylbromide, at an elevated temperature conveniently in the range of from100 to the boiling temperature of the reaction medium; a reactiontemperature of 130° to 150° C. is very suitable for this type ofreaction.

Furthermore, it is possible and, for some compounds of the invention,more convenient, to prepare certain compounds of formula I from othercompounds of formula I by standard techniques. Thus, for example, the SOor SO₂ oxides of compounds in which X¹ and X² are each sulphur may beprepared by conventional oxidation techniques; the N-alkyl analogues ofNH compounds may be prepared by standard alkylation procedures, e.g.using methyl iodide in triethylamine or with hydrogenation involving apalladium-carbon catalyst; and the 2-alkoxy compounds may be preparedfrom 2-chloro analogues using sodium alkoxide in methanol.

Therefore, the present invention further provides a process for thepreparation of a compound of general formula I, which comprises

a) to prepare symmetrical compounds in which R¹ =R¹⁰, R² =R⁹, R³ =R⁸ andR⁴ =R⁷ reacting under basic conditions a 4,6-dihalopyrimidine of thegeneral formula ##STR3## in which R⁵ and R⁶ are as defined above andeach of Hal¹ and Hal², independently, represents a halogen atompreferably chlorine or bromine, with a compound of the general formula##STR4## in which X represents a group CH₂ Hal, COHal, OH, SH or NRH,Hal represents a halogen atom, suitably chlorine or bromine, and R, R¹,R², R³ and R⁴ are as defined above, in a molar ratio of at least 1:2;

b) to prepare unsymmetrical compounds in which R¹, R², R³ and R⁴ are notthe same as R¹⁰, R⁹, R⁸ and R⁷ respectively, reacting under basicconditions a compound of formula II with a compound of formula III in amolar ratio of 1:1 and then reacting the resulting product with acompound of the general formula ##STR5## in which X, R⁷, R⁸, R⁹ and R¹⁰are as defined above, also in a molar ratio of 1:1; or

c) converting a compound of the general formula ##STR6## in which X¹,X², R¹, R², R³, R⁴, R⁶, R⁷, R⁸, R⁹ and R¹⁰ are as defined above, and R¹¹represents a group OH or NH₂, into a compound of general formula I,

and, if desired or required, converting one compound of formula I intoanother compound of formula I.

The prepared compounds of formula I may, if desired, be isolated andpurified using conventional techniques.

The compounds of formula II are either known or preparable by standardtechniques, for example by the conversion of a correspondingpyrimidinol, (prepared following the Principal synthesis from theappropriate malonate and formamidine under reflux and in the presence ofethanol and sodium ethanolate) using a phosphoryl halide, e.g. chloride,in triethylamine at elevated temperature, for example at 100° C., asdescribed in J. Org. Chem. 26, 1961, 4504.

Compounds of general formulae III and IV are either known or preparableby standard techniques, see for example J. Am. Chem. Soc. 73, 1951,3470, which describes conditions suitable for the preparation ofsuitable phenols from the corresponding anilines using sodium nitriteand aqueous sulphuric acid at 0° C. followed by steam distillation.

Compounds of general formula V, and alkyl derivatives thereof, with theexception of 2-amino-4,6-bisphenoxypyrimidine which is disclosed in J.Indian Chem. Soc. 53(9), 1976, 913-914, and2-amino-4,6-bis(3-chlorophenylimino)pyrimidine which is disclosed in J.Indian Chem. Soc. 52(8), 1975, 774-775, are believed to be novel andalso form part of the present invention. They may be prepared by methodsanalogous to that for the preparation of the compounds of formula I. The2-hydroxy-4,6-dihalo-pyrimidine precursor required for the preparationof compounds of formula V in which R¹¹ is hydroxy, may be prepared byprocedures described in Helv. Chim. Acta, 72, 1989, 738, from2,4,6-trihalopyrimidine reacted with dioxane in aqueous sodium hydroxidesolution at ambient temperature. The other precursor compounds may alsobe prepared using standard literature procedures. The prime use ofcompounds of formula V is in the preparation of compounds of formula I,however one or two of the novel compounds of formula V unexpectedlypossess pesticidal activity.

The compounds of the general formula I exhibit interesting and usefulpesticidal, particularly acaricidal, activity and as such can be used toadvantage to combat mites of the species Tetranychus and Panonychus.Moreover compounds of the present invention have been found to exhibitgood activity against mite species which have developed resistance toexisting commercial acaricides.

Certain compounds of the general formula I not only possess acaricidalactivity but also exhibit useful activity against insect pests includingwhitefly and mosquito.

Furthermore, it has been found that compounds of the general formula Iexhibit activity against animal ectoparasites, for example ticks onanimals such as cattle, sheep, goats, pigs, dogs, horses, deer and cats.

The present invention therefore also provides a pesticidal compositioncomprising a carrier, preferably two carriers at least one of which is asurface-active agent, and, as active ingredient, a compound of generalformula I. The invention additionally provides a method of combatingpests, being primarily acarid pests, at a locus which comprises treatingthe locus with a compound or composition of the invention, andspecifically provides the use as a pesticide, primarily as an acaricide,of a compound of general formula I. The dosage of active ingredient usedmay, for example, be from 5 to 500 ppm, preferably from 10 to 400 ppm,depending on the locus to be treated.

The present invention further provides a method of combating animalectoparasites which comprises applying on to the skin or coat of ananimal a compound of general formula I or a composition comprising sucha compound as active ingredient.

A carrier in a composition according to the invention is any materialwith which the active ingredient is formulated to facilitate applicationto the locus to be treated, which may for example be a plant, seed orsoil, or to facilitate storage, transport or handling. A carrier may bea solid or a liquid, including a material which is normally gaseous butwhich has been compressed to form a liquid, and any of the carriersnormally used in formulating pesticidal compositions may be used.Preferably compositions according to the invention contain 0.5 to 95% byweight of active ingredient.

Suitable solid carriers include natural and synthetic clays andsilicates, for example natural silicas such as diatomaceous earths;magnesium silicates, for example talcs; magnesium aluminium silicates,for example attapulgites and vermiculites; aluminium silicates, forexample kaolinires, montmorillonites and micas; calcium carbonate;calcium sulphate; ammonium sulphate; synthetic hydrated silicon oxidesand synthetic calcium or aluminium silicates; elements, for examplecarbon and sulphur; natural and synthetic resins, for example coumaroneresins, polyvinyl chloride, and styrene polymers and copolymers; solidpolychlorophenols; bitumen; waxes; and solid fertilisers, for examplesuperphosphates.

Suitable liquid carriers include water; alcohols, for exampleisopropanol and glycols; ketones, for example acetone, methyl ethylketone, methyl isobutyl ketone and cyclohexanone; ethers; aromatic oraraliphatic hydrocarbons, for example benzene, toluene and xylene;petroleum fractions, for example kerosine and light mineral oils;chlorinated hydrocarbons, for example carbon tetrachloride,perchloroethylene and trichloroethane. Mixtures of different liquids areoften suitable.

Agricultural compositions are often formulated and transported in aconcentrated form which is subsequently diluted by the user beforeapplication. The presence of small amounts of a carrier which is asurface-active agent facilitates this process of dilution. Thuspreferably at least one carrier in a composition according to theinvention is a surface-active agent. For example the composition maycontain at least two carriers, at least one of which is a surface-activeagent.

A surface-active agent may be an emulsifying agent, a dispersing agentor a wetting agent; it may be nonionic or ionic. Examples of suitablesurface-active agents include the sodium or calcium salts of polyacrylicacids and lignin sulphonic acids; the condensation products of fattyacids or aliphatic amines or amides containing at least 12 carbon atomsin the molecule with ethylene oxide and/or propylene oxide; fatty acidesters of glycerol, sorbitol, sucrose or pentaerythrltol; condensates ofthese with ethylene oxide and/or propylene oxide; condensation productsof fatty alcohol or alkyl phenols, for example p-octylphenol orp-octylcresol, with ethylene oxide and/or propylene oxide; sulphates orsulphonates of these condensation products; alkali or alkaline earthmetal salts, preferably sodium salts, of sulphuric or sulphonic acidesters containing at least 10 carbon atoms in the molecule, for examplesodium lauryl sulphate, sodium secondary alkyl sulphates, sodium saltsof sulphonated castor oil, and sodium alkylaryl sulphonates such asdodecylbenzene sulphonate; and polymers of ethylene oxide and copolymersof ethylene oxide and propylene oxide.

The compositions of the invention may for example be formulated aswettable powders, dusts, granules, solutions, emulsifiable concentrates,emulsions, suspension concentrates and aerosols. Wettable powdersusually contain 25, 50 or 75% w of active ingredient and usually containin addition to solid inert carrier, 3-10% w of a dispersing agent and,where necessary, 0-10% w of stabiliser(s) and/or other additives such aspenetrants or stickers. Dusts are usually formulated as a dustconcentrate having a similar composition to that of a wettable powderbut without a dispersant, and are diluted in the field with furthersolid carrier to give a composition usually containing 1/2-10% w ofactive ingredient. Granules are usually prepared to have a size between10 and 100 BS mesh (1.676-0.152 mm), and may be manufactured byagglomeration or impregnation techniques. Generally, granules willcontain 1/2-75% w active ingredient and 0-10% w of additives such asstabilisers, surfactants, slow release modifiers and binding agents. Theso-called "dry flowable powders" consist of relatively small granuleshaving a relatively high concentration of active ingredient.Emulsifiable concentrates usually contain, in addition to a solvent and,when necessary, co-solvent, 10-50% w/v active ingredient, 2-20% w/vemulsifiers and 0-20% w/v of other additives such as stabilisers,penetrants and corrosion inhibitors. Suspension concentrates are usuallycompounded so as to obtain a stable, non-sedimenting flowable productand usually contain 10-75% w active ingredient, 0.5-15% w of dispersingagents, 0.1-10% w of suspending agents such as protective colloids andthixotropic agents, 0-10% w of other additives such as defoamers,corrosion inhibitors, stabilisers, penetrants and stickers, and water oran organic liquid in which the active ingredient is substantiallyinsoluble; certain organic solids or inorganic salts may be presentdissolved in the formulation to assist in preventing sedimentation or asanti-freeze agents for water.

Aqueous dispersions and emulsions, for example compositions obtained bydiluting a wettable powder or a concentrate according to the inventionwith water, also lie within the scope of the invention. The saidemulsions may be of the water-in-oil or of the oil-in-water type, andmay have a thick `mayonnaise`-like consistency.

The composition of the invention may also contain other activeingredients, for example insecticides or fungicides, or, in appropriatecircumstances, herbicides. The compounds of formula I may be found to beespecially useful when applied in admixture with other insecticidesand/or acaricides, e.g. organophosphates, pyrethroids, carbamates, acylureas and organotin compounds, for example the commercial productsazinphos-methyl, chlorpyriphos, phosalone, fenpropathin, bifenthrin,pirimicarb, triazamate, diflubenzuron, flufenoxuron, teflubenzuron andfenbutatin oxide. Other mixture partners which, with the compounds ofthe invention may yield useful control, are amitraz, hexythiazox,pyridaben, and fenpyroximate.

The following Examples illustrate the invention. Examples 1 and 2illustrate the preparation of starting materials of formulae III and IIrespectively; Examples 3 to 6 illustrate the preparation of compounds offormula I.

EXAMPLE 1 Preparation of 4-bromo-3-trifluoromethylphenol

4-Bromo-3-trifluoromethylaniline (48 g, 0.2 mol) was treated with water(300 ml) and concentrated H₂ SO₄ (36 ml) at 60° C. for 1 hour. Theresulting suspension was cooled in an ice bath and treated with sodiumnitrite (16 g, 0.23 mol) in water (30 ml) maintaining the temperature ofthe reaction mixture below 10° C. The resulting solution was stirred at0° C. for 1 hour, and then added portionwise, over 1 hour, to a 25% H₂SO₄ aqueous solution (160 ml) whilst steam distilling. After collectingapproximately 1 liter of distillate, the aqueous distillate wasextracted with ether and the organic solution dried using MgSO₄,filtered and concentrated. The product, 4-bromo-3-trifluoromethylphenol,was obtained by distillation under reduced pressure. Yield 18.0 g (37%);boiling point 68-71/1 mmHg.

Elemental Analysis (%): Calculated: C 34.9 H 1.7

Found: C 34.9 H 1.7

EXAMPLE 2 Preparation of 4,6-dichloro-2-trifluoromethylpyrimidine

Sodium (13 g, 0.57 mol) was dissolved in ethanol (500 ml) and diethylmalonate (84 g, 0.53 mol) was added, followed bytrifluoromethylformamidine (62 g, 0.55 mol). The mixture was heatedunder reflux for 12 hours. On cooling, the mixture was concentratedunder reduced pressure, and the product was taken up in water. Onacidification with concentrated HCl, the product precipitated and wascollected. Yield: 27.5 g (28%).

The precipitate (5.0 g, 0.028 mol) was suspended in triethylamine (20ml) and was treated carefully with POCl₃ (20 ml). After the exotherm hadsubsided, the reaction mixture was heated at 100° C. for 2 hours, andthen cooled and poured onto ice. The product was extracted into diethylether, dried over Na₂ SO₄ and concentrated under reduced pressure. Thefinal product, 4,6-dichloro-2-trifluoromethylpyrimidine, was obtained bybulb-to-bulb distillation. Yield: 3.2 g (52%); boiling point: 120° C./20mmHg.

EXAMPLE 3 Preparation of4,6-bis(4-chloro-3-trifluoromethylphenoxy)pyrimidine

4-Chloro-3-trifluoromethylphenol (10.0 g, 0.051 mol) and4,6-dichloropyrimidine (3.7 g, 0.025 mol) were heated to 60° C. indimethylsulphoxide (75 ml) with potassium carbonate (10 g) undernitrogen for 12 hours. The mixture was then poured into water and theproduct extracted into diethyl ether. The organic layer was dried usingNa₂ SO₄, filtered and concentrated. The product,4,6-bis(4-chloro-3-tri-fluoromethylphenoxy)pyrimidine, was obtained bycolumn chromatography (eluting with 5:1, hexane:ethyl acetate) andrecrystallization (diethyl ether/hexane). Yield 11.0 g (94%); meltingpoint 111° C.

Elemental Analysis (%):

Calculated: C 46.1 H 1.7N 6.0

Found: C 47.3 H 1.8N 5.9

EXAMPLE 4 Preparation of4,6-bis(3-trifluoromethylphenoxy)-2-bromo-pyrimidine

a) Preparation of 4,6-bis(3-trifluoromethylphenoxy)pyrimidin-2-one

Sodium hydroxide (20 g, 0.5 mol) in water (160 ml) was added to asolution of 2,4,6-tri-chloropyrimidine (36.7g, 0.2 mol) in dioxane (600ml). The mixture was stirred for 4 hours to give a thick whiteprecipitate. The mixture was concentrated in vacuo and the residuerecrystallized from boiling water. Yield: 18 g (55%).

The residue, 4,6-dichloropyrimidin-2-one, (8.0 g, 0.049 mol) and3-trifluoromethylphenol (20 g, 0.123 mol) were heated indimethylformamide (250 ml) with potassium carbonate (16 g) undernitrogen at 100° C. for 12 hours. The mixture was then poured into waterand the precipitate collected. The product,4,6-bis(3-trifluoro-methylphenoxy)pyrimidin-2-one, was obtained byrecrystallization from methanol/water and column chromatography (elutingwith 1:1, hexane:ethyl acetate). Yield: 2.5 g (12%).

Elemental Analysis (%):

Calculated: C 44.6 H 1.7N 5.8

Found: C 45.7 H 2.1N 5.7

b) Preparation of 4,6-bis(3-trifluoromethylphenoxy)-2-bromo-pyrimidine

4,6-Bis(3-trifluoromethylphenoxy)-pyrimidin-2-one (4.0 g, 0.0096 mol)and POBr₃ (100g) were heated at 140° C. for 48 hours. The mixture wasthen poured onto a mixture of 2N NaOH (500 ml) and ice. The product wasextracted into diethyl ether, dried using Na₂ SO₄, filtered andconcentrated under reduced pressure. The product was obtained by columnchromatography (3:1, hexane: ethyl acetate) and recrystallization (ethylacetate/hexane). Yield: 1.0 g (22%); melting point 126°-129° C.

Elemental Analysis (%):

Calculated: C 45.1 H1.9N5.9

Found: C 45.7 H2.1N6.1

EXAMPLE 5 Preparation of4,6-bis<4-fluoro-3-trifluoromethyl-phenoxyl)-2-chloro-pyrimidine

2-Amino-4,6-bis(4-fluoro-3-trifluoromethylphenoxy)pyrimidine (3.0 g, 6.7mmol) was dissolved in carbon tetrachloride (75 ml) and the resultingsolution was treated with t-butylnitrite (1.2 ml, 13.4 mmol). Themixture was heated at 30° C. for 48 hours and then poured into water.The product was extracted in dichloromethane, dried over sodiumsulphate, filtered and concentrated under reduced pressure. The product,4,6-bis(4-fluoro-3-trifluoromethyl-phenoxy)-2-chloro-pyrimidine, wasobtained as an oil by column chromatography (eluting with 5:1,hexane:ethyl acetate). Yield 0.3 g (10%); mass 471 (M⁺ +H); N.m.r:7.3-7.5 (6H, m, aromatics), 6.35 (1H,s,H-5).

Elemental Analysis (%):

Calculated: C 49.6 H 1.9N 6.4

Found: C 49.8 H 2.1N 6.4

EXAMPLE 6 Preparation of4-(4-cyanophenoxy)-6-<4-fluoro-3-trifluoromethyl-phenoxy)-pyrimidine

a) Preparation of4-fluoro-6-<4-fluoro-3-trifluoromethylphenoxy)pyrimidine

4,6-difluoropyrimidine (2.0 g, 0.017 mol) was placed indimethylformamide (150 cm³) with potassium carbonate (2.5 g) and thetemperature reduced to about -20° C. 4-fluoro-3-trifluoro-methylphenol(2.9 g in 25 cm³ of dimethylformamide) was then added dropwise over 2hours. The mixture was then left to stir for 4 hours between -30° and-20° C. After this time gas chromatography showed the reaction to beincomplete, so the mixture was left in the freezer overnight to preventit from reaching room temperature. The mixture was then left to stir fora further 5 hours at -20° C. after which time gas chromatography showedno further reaction. The mixture was then poured into water, theresultant solid filtered and recrystallised from cyclohexane. Yield 0.9g (21%):

Calculated: C 47.8 H 1.8N 10.1

Found: C 48.0 H 2.2N 10.1

A further 0.5 g of product was recovered from the recrystallisationfiltrate, to give a total yield of 31%.

b) Preparation of4-(4-cyanophenoxy)-6-(4-fluoro-3-trifluoro-methylphenoxy)-pyrimidine

4-fluoro-6-(4-fluoro-3-trifluoromethylphenoxy)-pyrimidine (0.9 g, 3.3mmol) was placed in dimethylformamide (100 cm³) with potassium carbonate(0.6 g) and the temperature reduced to 0° C. 4-cyanophenol (0.37 g in 20cm³ dimethylformamide) was then added dropwise and the mixture left tostir whilst maintaining the temperature at <5° C. for 6 hours. Afterthis time gas chromatography showed little or no reaction so a further0.2 equivalent of 4-cyanophenol was added, and the mixture left to stirovernight with the temperature reaching room temperature. After thistime, gas chromatography and thin layer chromatography showed thereaction to be complete, so the mixture was poured into 100 cm³ of waterand the resultant solid filtered and recrystallised from cyclohexane.Yield 0.93 g (75%); melting point 131°-132° C.

Calculated: C 57.6 H 2.4N 11.2

Found: C 57.5 H 2.6 N 11.2

EXAMPLES 7 TO 63

By methods analogous to those of Examples 3 to 6, further compounds offormula I were prepared. Details are given in Table I below, withreference to the following formula: ##STR7##

R⁴ and R⁷ are each hydrogen.

                                      TABLE 1                                     __________________________________________________________________________                                              Melting   Elemental Analysis                                                  Point     (% Calc./Found)           Ex. No.                                                                            R.sup.1                                                                         R.sup.2                                                                          R.sup.3                                                                            X.sup.1                                                                          R.sup.5                                                                            R.sup.6                                                                          X.sup.2                                                                          R.sup.8                                                                            R.sup.9                                                                            R.sup.10                                                                         (°C.)                                                                            C   H  N                  __________________________________________________________________________    7    H H  CF.sub.3                                                                           O  H    H  O  CF.sub.3                                                                           H    H  72.0      54.0                                                                              2.5                                                                              7.0                                                                    54.2                                                                              2.6                                                                              7.4                8    H H  CF.sub.3                                                                           S  H    H  S  CF.sub.3                                                                           H    H  157.0     50.0                                                                              2.3                                                                              6.5                                                                    50.4                                                                              2.2                                                                              7.0                9    H H  CF.sub.3                                                                           NH H    H  NH CF.sub.3                                                                           H    H  195.0     54.3                                                                              3.0                                                                              14.1                                                                   54.1                                                                              3.5                                                                              14.4               10   H H  CF.sub.3                                                                           O  H    CH.sub.3                                                                         O  CF.sub.3                                                                           H    H  82.3      55.1                                                                              2.9                                                                              6.8                                                                    54.9                                                                              3.1                                                                              6.7                11   H H  OCF.sub.3                                                                          O  H    H  O  OCF.sub.3                                                                          H    H  oil       50.0                                                                              2.3                                                                              6.5                                                                    51.0                                                                              2.6                                                                              6.6                12   H H  CF.sub.3                                                                           O  SCH.sub.3                                                                          H  O  CF.sub.3                                                                           H    H  86.4      51.1                                                                              2.7                                                                              6.3                                                                    50.9                                                                              2.9                                                                              6.2                13   H H  CF.sub.3                                                                           O  CH.sub.3                                                                           H  O  CF.sub.3                                                                           H    H  104.9     55.1                                                                              2.9                                                                              6.8                                                                    56.1                                                                              3.0                                                                              6.8                14   H H  CF.sub.3                                                                           O  SC.sub.2 H.sub.5                                                                   H  O  CF.sub.3                                                                           H    H  48.7      52.2                                                                              3.0                                                                              6.1                                                                    52.1                                                                              3.2                                                                              6.1                15   H H  CF.sub.3                                                                           O  SOC.sub.2 H.sub.5                                                                  H  O  CF.sub.3                                                                           H    H  82.9      50.4                                                                              2.9                                                                              5.9                                                                    50.4                                                                              3.2                                                                              5.8                16   H H  Cl   O  H    H  O  Cl   H    H  oil       57.9                                                                              3.0                                                                              8.4                                                                    55.3                                                                              3.7                                                                              5.1                17   H H  CF.sub.3                                                                           O  H    H  O  H    H    H  89.0      61.4                                                                              3.3                                                                              8.4                                                                    61.1                                                                              3.5                                                                              8.1                18   H NO.sub.2                                                                         CF.sub.3                                                                           O  H    H  O  CF.sub.3                                                                           NO.sub.2                                                                           H  136.0     44.1                                                                              1.6                                                                              11.4                                                                   45.0                                                                              2.0                                                                              11.3               19   H H  CF.sub.3                                                                           O  H    H  O  F    H    H  47.0      58.3                                                                              2.9                                                                              8.0                                                                    58.8                                                                              3.1                                                                              8.1                20   H H  CF.sub.3                                                                           O  H    H  O  Cl   H    H  78.0      55.7                                                                              2.7                                                                              7.6                                                                    55.4                                                                              2.8                                                                              7.7                21   H H  CF.sub.3                                                                           O  H    H  O  CH.sub.3                                                                           H    H  61.0      62.4                                                                              3.8                                                                              8.1                                                                    62.3                                                                              4.0                                                                              7.9                22   H H  C.sub.2 F.sub.5                                                                    O  H    H  O  C.sub.2 F.sub.5                                                                    H    H  oil       48.0                                                                              2.0                                                                              5.6                                                                    48.4                                                                              2.3                                                                              5.7                23   F H  CF.sub.3                                                                           O  H    H  O  CF.sub.3                                                                           H    F  70.0      49.5                                                                              1.8                                                                              6.4                                                                    51.5                                                                              1.9                                                                              6.3                24   H H  CF.sub.3                                                                           O  Cl   H  O  CF.sub.3                                                                           H    H  108-111   49.7                                                                              2.1                                                                              6.4                                                                    50.1                                                                              2.1                                                                              6.5                25   H Br CF.sub.3                                                                           O  H    H  O  CF.sub.3                                                                           Br   H  119.3-121.4                                                                             38.7                                                                              1.5                                                                              5.0                                                                    38.9                                                                              1.8                                                                              5.1                26   H Cl CF.sub.3                                                                           O  Cl   H  O  CF.sub.3                                                                           Cl   H  135-136   42.9                                                                              1.4                                                                              5.6                                                                    43.4                                                                              1.6                                                                              5.5                27   H F  CF.sub.3                                                                           O  H    H  O  CF.sub.3                                                                           F    H  200° C.*/0.6                                                                     49.6                                                                              1.8                                                                              6.4                                                                    49.9                                                                              2.4                                                                              5.6                28   H Cl CF.sub.3                                                                           O  SCH.sub.3                                                                          H  O  CF.sub.3                                                                           Cl   H  110.4-110.5                                                                             44.4                                                                              2.0                                                                              5.3                                                                    44.7                                                                              2.3                                                                              5.4                29   H CN CF.sub.3                                                                           O  H    H  O  CF.sub.3                                                                           CN   H  132.0-138.0                                                                             53.3                                                                              1.8                                                                              12.4                                                                   53.3                                                                              2.4                                                                              12.4               30   H H  H    O  H    H  O  H    H    H  109.5     72.7                                                                              4.5                                                                              10.6                                                                   73.6                                                                              4.8                                                                              11.0               31   H H  H    O  SCH.sub.3                                                                          H  O  H    H    H  109.6     65.8                                                                              4.5                                                                              9.0                                                                        4.5                                                                              8.9                32   H Cl CF.sub.3                                                                           O  CF.sub.3                                                                           H  O  CF.sub.3                                                                           Cl   H  116-120   42.5                                                                              1.3                                                                              5.2                                                                    43.5                                                                              2.2                                                                              4.9                33   H Cl CF.sub.3                                                                           O  F    H  O  CF.sub.3                                                                           Cl   H  126.6-127.1                                                                             44.4                                                                              1.6                                                                              5.8                                                                    44.3                                                                              1.9                                                                              5.7                34   H H  CF.sub.3                                                                           O  C.sub.6 H.sub.5                                                                    H  O  CF.sub.3                                                                           H    H  84.0-85.0 60.5                                                                              3.0                                                                              5.9                                                                    60.4                                                                              3.3                                                                              5.7                35   H NO.sub.2                                                                         H    O  H    H  O  CF.sub.3                                                                           H    H  126.0-127.0                                                                             54.2                                                                              2.7                                                                              11.2                                                                   54.2                                                                              2.7                                                                              12.0               36   H F  H    O  H    H  O  CF.sub.3                                                                           H    H  117.9-118.4                                                                             59.0                                                                              2.9                                                                              8.0                                                                    60.5                                                                              2.9                                                                              8.7                37   H F  CF.sub.3                                                                           O  SCH.sub.3                                                                          H  O  CF.sub.3                                                                           F    H  97.0-98.0 47.3                                                                              2.1                                                                              5.8                                                                    48.0                                                                              2.6                                                                              6.0                38   H Cl CF.sub.3                                                                           O  F    H  O  CF.sub.3                                                                           Cl   H  129.0-130.0                                                                             44.4                                                                              1.4                                                                              5.7                                                                    44.3                                                                              1.7                                                                              5.7                39   H F  H    O  H    H  O  CF.sub.3                                                                           F    H  122.0-123.0                                                                             56.0                                                                              2.2                                                                              7.6                                                                    57.3                                                                              2.9                                                                              7.7                40   H H  CF.sub.3                                                                           O  H    H  O  H    CN   H  196.0-197.0                                                                             60.6                                                                              2.8                                                                              11.7                                                                   59.4                                                                              3.0                                                                              10.6               41   H CN CF.sub.3                                                                           O  SCH.sub.3                                                                          H  O  CF.sub.3                                                                           CNH  H  148.0-149.0                                                                             50.3                                                                              2.4                                                                              11.3                                                                   51.1                                                                              2.4                                                                              11.2               42   H F  CF.sub.3                                                                           O  C.sub.6 H.sub.5                                                                    H  O  CF.sub.3                                                                           F    H  78.0-79.0 56.3                                                                              2.4                                                                              5.5                                                                    56.0                                                                              2.5                                                                              5.3                43   H H  C.sub.2 F.sub.5                                                                    O  SCH.sub.3                                                                          H  O  C.sub.2 F.sub.5                                                                    H    H  61.0-62.0 46.1                                                                              2.2                                                                              5.1                                                                    46.1                                                                              2.4                                                                              5.1                44   H H  CH--CF.sub.2                                                                       O  H    H  O  CH--CF.sub.2                                                                       H    H  oil       --                        45   H F  CF.sub.3                                                                           O  H    H  O  CF.sub.3                                                                           H    H  57.0-58.0 51.8                                                                              2.4                                                                              6.7                                                                    51.8                                                                              2.4                                                                              6.7                46   H F  CF.sub.3                                                                           O  H    H  O  H    NO.sub.2                                                                           H  oil       51.7                                                                              2.3                                                                              10.6                                                                   51.5                                                                              2.5                                                                              10.5               47   H Br CF.sub.3                                                                           O  Cl   H  O  CF.sub.3                                                                           Br   H  192.0-193.0                                                                             36.5                                                                              1.2                                                                              4.7                                                                    36.3                                                                              1.5                                                                              4.7                48   H F  CF.sub.3                                                                           O  H    H  O  H    Cl   H  oil       53.1                                                                              2.3                                                                              7.3                                                                    53.5                                                                              2.6                                                                              7.3                49   H F  CF.sub.3                                                                           O  H    H  O  Cl   H    H  61.9-62.7 53.1                                                                              2.3                                                                              7.3                                                                    53.3                                                                              2.6                                                                              7.2                50   H F  CF.sub.3                                                                           O  H    H  O  F    H    H  oil       55.4                                                                              2.4                                                                              7.6                                                                    55.6                                                                              2.6                                                                              7.6                51   H F  CF.sub.3                                                                           O  H    H  O  CH.sub.3                                                                           H    H  oil       59.3                                                                              3.3                                                                              7.3                                                                    59.6                                                                              3.4                                                                              7.7                52   H H  C.sub.2 F.sub.5                                                                    O  Cl   H  O  C.sub.2 F.sub.5                                                                    H    H  85.0-87.0 44.9                                                                              1.7                                                                              5.2                                                                    44.6                                                                              2.1                                                                              5.3                53   H F  CF.sub.3                                                                           O  H    H  O  CF.sub.3                                                                           Cl   H  68.0      47.7                                                                              1.8                                                                              6.2                                                                    47.4                                                                              2.0                                                                              6.1                54   H F  CF.sub.3                                                                           O  H    H  O  C(CH.sub.3).sub.3                                                                  H    H  69.7-71.6 62.1                                                                              4.4                                                                              6.9                                                                    62.9                                                                              4.8                                                                              6.9                55   H F  CF.sub.3                                                                           O  H    H  O  H    C(CH.sub.3).sub.3                                                                  H  104.6-105.1                                                                             62.1                                                                              4.4                                                                              6.9                                                                    62.4                                                                              4.8                                                                              6.9                56   H F  CF.sub.3                                                                           O  H    H  O  NO.sub.2                                                                           H    H  103.0-103.2                                                                             51.6                                                                              2.3                                                                              10.6                                                                   51.4                                                                              2.5                                                                              10.6               57   H H  CF.sub.3                                                                           O  H    H  O  CF.sub.3                                                                           Cl   H  oil           --                    58   H F  CF.sub.3                                                                           O  H    H  O  CN   H    H  80.9-81.3 57.6                                                                              2.4                                                                              11.2                                                                   57.1                                                                              2.7                                                                              11.2               59   H F  CF.sub.3                                                                           O  H    H  O  CO.sub.2 CH.sub.3                                                                  H    H  71.0-72.0 55.9                                                                              3.0                                                                              6.9                                                                    55.8                                                                              3.2                                                                              6.9                60   H F  CF.sub.3                                                                           O  SCH.sub.3                                                                          H  O  CF.sub.3                                                                           H    H  86.5-87.2 49.0                                                                              2.4                                                                              6.0                                                                    48.7                                                                              2.7                                                                              6.3                61   H Br CF.sub.3                                                                           O  H    H  O  CF.sub.3                                                                           H    H  oil       45.1                                                                              2.0                                                                              5.8                                                                    45.0                                                                              2.4                                                                              5.9                62   H Br CF.sub.3                                                                           O  H    H  O  CF.sub.3                                                                           F    H  oil       43.5                                                                              1.6                                                                              5.6                                                                    43.9                                                                              2.0                                                                              5.6                63   H F  CF.sub.3                                                                           O  Cl   H  O  CF.sub.3                                                                           H    H  105.3-105.5                                                                             47.8                                                                              1.8                                                                              6.2                                                                    46.7                                                                              2.1                                                                              6.2                __________________________________________________________________________     *boiling point                                                           

EXAMPLES 64 TO 67

By methods analogous to those of Examples 3 to 6, further compounds offormula I were prepared. Details are given in Table II below, withreference to the following formula:

                  TABLE II                                                        ______________________________________                                         ##STR8##                                                                                         Elemental Analysis                                                     Melting                                                                              (% Calc./Found)                                           Ex No.   R.sup.7   Point (°C.)                                                                     C      H    N                                     ______________________________________                                        64       Cl        oil      53.1   2.3  7.3                                                               53.2   2.9  6.9                                   65       F         73.0-73.1                                                                              55.4   2.4  7.6                                                               55.7   2.7  7.5                                   66       C(CH.sub.3).sub.3                                                                       oil      52.1   4.4  6.9                                                               52.7   4.8  6.6                                   67       CH.sub.3  oil      59.3   3.3  7.7                                                               59.7   3.3  7.4                                   ______________________________________                                    

EXAMPLE 68

Acaricidal Activity

The acaricidal activity of the compounds of the invention was determinedin the following tests employing the glasshouse red spider mite,Tetranychus urticae (T.u.).

In each test solutions or suspensions of test compound were made up overa range of concentrations in water (initially O.1%w) containing 10%wacetone and 0.025% w "TRITON X-100" (trade mark) surface active agent(the condensation product of ethylene oxide with an alkyl phenol). Thesesolutions were sprayed at a rate equivalent to 340 liters per hectare(3.4×10⁻⁵ m³ /m²) onto petri dishes containing either test species perse or diet onto which test species were subsequently introduced, asindicated. The tests were all conducted under normal insectaryconditions (23° C.±2° C., fluctuating humidity and 16 hours day lengthlight).

The results of testing at the initial test concentrations were graded:

Grade A represents at least 70% mortality of the pest

Grade B represents from 40% to 69% mortality.

For compounds achieving Grade A at initial test concentration, mortalityassessments were made as indicated below, in terms of percentagemortality figures. In each test a LC₅₀ (the dosage of active materialrequired to kill half of the test species) for the compound wascalculated from the mortality figures and compared with thecorresponding LC₅₀ for a standard insecticide (either ethyl parathion orchlorfenson, as indicated) in the same test. The results are expressedas toxicity indices thus: ##EQU1## a) Acaricidal activity--mite adultsTu

Acaricidal activity was assessed using adult glasshouse red spidermites, Tetranychus urticae (T.u.), 7-10 days after hatching, by thefollowing procedure:

2 cm diameter discs cut from the leaves of French bean plants wereplaced on filter paper kept moist by a cotton wool wick dipped intowater. Prior to testing, each leaf disc was infested with 10 adultmites. The mites and discs were then sprayed with solutions of the testcompound made up as above, at a rate equivalent to 340 liters perhectare (3.4×10⁵ m³ /m²). The mites were held under the normal insectaryconditions. The numbers of dead and moribund adults were assessed after48 hours and the percentage mortality calculated.

b) Acaricidal activity--ovicide TuOA

Acaricidal activity was assessed employing eggs of the glasshouse redspider mite, Tetranychus urticae (T.u.), less than 24 hours old, by thefollowing procedure.

2 cm diameter leaf discs cut from the leaves of French bean plants wereplaced on filter paper, kept moist by a cotton wool wick dipped intowater.

On the day before spraying, each leaf disc was infested with 10 femaleadult mites. On the day of the test, the adults were removed, leavingthe eggs laid overnight on the discs. The leaf discs were then sprayedwith solutions of test compound made up as above, at a rate equivalentto 340 liters per hectare (3.4×10⁻⁵ m³ /m²).

Throughout the test, the eggs were held under the normal insectaryconditions. After 7-10 days, the numbers of hatched nymphs and unhatchedeggs were assessed and the percentage mortality calculated.

The LC₅₀ (the dosage of active material required to kill half of thetest species) for each test compound was calculated from the mortalityfigure and compared with the corresponding LC₅₀ for a standardinsecticide in the same test. For Tu ethyl parathion was used as thestandard compound; for TuOA chlorfenson was used as the standard.

The results are given in Table III below.

                  TABLE III                                                       ______________________________________                                        Acaricidal Activity                                                                             Toxicity Index                                              Compound of Example No.                                                                           Tu     Tu OA                                              ______________________________________                                        3                   320    720                                                4                   67                                                        5                   400    1400                                               6                   12     140                                                7                   75     94                                                 8                   5                                                         9                   <4     <20                                                10                         B                                                  11                  <3                                                        12                  28     66                                                 13                  5                                                         14                  23     63                                                 15                         <18                                                16                  5      20                                                 17                         41                                                 18                  70     34                                                 19                  10                                                        20                  27     35                                                 21                  4      12                                                 22                  100    41                                                 23                  4                                                         24                  170    <16                                                25                  98     180                                                26                  150    180                                                27                  360    2200                                               28                  18     B                                                  29                  62     250                                                30                         <23                                                31                         <12                                                32                  22     73                                                 33                  60     200                                                34                  11     <19                                                35                  25     <16                                                36                  21     60                                                 37                  190    730                                                38                  100                                                       39                  42     390                                                40                  35     87                                                 41                  10     94                                                 42                  36     20                                                 43                         57                                                 44                         36                                                 45                  110    640                                                46                  73     100                                                47                  18                                                        48                  21     160                                                49                  77     190                                                50                  24     170                                                51                  38     65                                                 52                  100    130                                                53                  760    1500                                               54                  29     81                                                 55                  11     62                                                 56                  128    700                                                57                  94     870                                                58                  72     650                                                59                  6      <4                                                 60                  65     A                                                  61                  57     A                                                  62                  130    A                                                  63                  120    760                                                64                  2      <27                                                65                  10     50                                                 66                  11     57                                                 67                  19     100                                                ______________________________________                                    

EXAMPLE 69

Comparison Tests

The acaricidal activity of the prior art compound2-amino-4,6-bisphenoxypyrimidine and of the 2-amino analogues of thesubstituted pyrimidines of Examples 3 and 7 was determined following theprocedures of Example 68 above. The results are given in Table IV below,and for ease of comparison the data for the compounds of Examples 3 and7 are also included in the Table.

                  TABLE IV                                                        ______________________________________                                                       Toxicity Index                                                 Compound         Tu     TuOA                                                  ______________________________________                                        Example 3        320    720                                                   Example 7        75     94                                                    Comparison A     C      C                                                     Comparison B     C      C                                                     Comparison C     C      C                                                     ______________________________________                                    

Comparison A is the 2-amino analogue of the compound of Example 3, andComparison B is the 2-amino analogue of the compound of Example 7.Comparison C is 2-amino-4,6-bisphenoxy-pyrimidine. Grade C representsless than 40% mortality of the pest, whereas the Toxicity Index is onlyestimated when Grade A activity (i.e. at least 70% mortality) isachieved.

It can clearly be seen that the compounds of the present invention havea significantly greater acaricidal activity than the direct 2-aminoanalogues.

EXAMPLE 70

Insecticidal Activity

Insecticidal activity of compounds of general formula I was assessedagainst the following pest:

Trialeurodes vaporariorum (greenhouse whitefly) (T.v.)

The test method employed appears below. In each test, solutions orsuspensions of test compound were made up and sprayed as described abovein Example 68.

French bean plants (Phaseolus vulgaris) with two fully expanded leaveswere placed in a breeding culture of T. vaporariorum, also on Frenchbean plants, which were then disturbed to ensure resettlement on theintroduced plants. During the subsequent 24 hour period, eggs weredeposited and kept at 27° C., with 14 hours photoperiod. All adultwhiteflies were then carefully removed, leaving egg samples of a knownage. After eight days the majority of eggs had hatched. Leaf discscontaining the newly hatched nymphs were then cut from the leaves andtransferred to moist filter paper. The discs were examined under alow-powered microscope to determine the exact number of 1st instarnymphs per disc and to remove any unhatched eggs. On average, 70-100nymphs were found per disc. The discs were transferred into Petri dishesand sprayed with test solutions as described above. After 6 dayspercentage mortalities were assessed.

The LC₅₀ for each test compound was calculated as described above inExample 68. Ethyl parathion was used as the standard compound. Theresults are given in Table V below.

                  TABLE V                                                         ______________________________________                                        Insecticidal Activity                                                                           Toxicity Index                                              Compound of Example No.                                                                         T.v.                                                        ______________________________________                                        5                 320                                                         22                180                                                         27                95                                                          36                <20                                                         37                190                                                         39                95                                                          45                370                                                         48                17                                                          49                27                                                          ______________________________________                                    

EXAMPLE 71

Ectoparasiticidal Activity

In tests on tick larvae, Boophilus decoloratus, a concentration range of1-25 ppm of the compound of Example 27 was used. Dead larvae weredetected after 24 hours with all the concentrations, with the highestmortality occurring with the 25 ppm concentration. After 40 hours, nolive larvae were observed with the 25 ppm concentration.

We claim:
 1. A compound having the structural formula ##STR9## whereinX¹ and X² are the same and each represents an oxygen atom; a groupS(O)_(n) in which n is 0, 1 or 2; or a group CO, CH₂ or NR in which Rrepresents a hydrogen atom or a C₁₋₆ alkyl group;R¹ and R¹⁰ are the sameor different and each represents a hydrogen atom or a halogen atom; R²and R⁹ are the same or different and each represents a hydrogen atom, ahalogen atom or a cyano, nitro, C₁₋₆ alkyl, haloC₁₋₆ alkyl, C₁₋₆ alkoxy,C₁₋₆ alkylthio, amino, mono- or di(C₁₋₆ alkyl)amino, C₁₋₆ alkoxyC₁₋₆alkyl, haloC₁₋₆ alkoxyC₁₋₆ alkyl or (C₁₋₆ alkoxy) carbonyl group; R³ andR⁸ are the same or different and each represents a hydrogen atom, achlorine atom, or a C₁₋₆ alkyl, haloC₁₋₆ alkyl, haloC₁₋₆ alkoxy,haloC₁₋₆ alkylthio, haloC₂₋₆ alkenyl, haloC₂₋₆ alkynyl, haloC₁₋₆alkoxyC₁₋₆ alkyl, (haloC₁₋₆ alkoxy) carbonyl, haloC₁₋₆ alkylsulphinyl,haloC₁₋₆ alkylsulphonyl, nitro or cyano group; R⁴ and R⁷ are the same ordifferent and each represents a hydrogen atom, a halogen atom or a C₁₋₆alkyl or C₁₋₆ alkoxy group; R⁵ represents a hydrogen atom, a halogenatom, or a cyano, C₁₋₆ alkyl, haloC₁₋₆ alkyl, C₁₋₆ alkoxy, C₁₋₆alkylthio, C₁₋₆ alkylsulphinyl or phenyl group; and R⁶ represents ahydrogen atom or, when R⁵ is hydrogen, a C₁₋₆ alkyl group; provided thatat least one of R³ and R⁸ is other than hydrogen.
 2. The compoundaccording to claim 1 whereineach of X¹ and X² represents an oxygen atom,a sulphur atom or a group NH; R¹ and R¹⁰ are the same and eachrepresents a hydrogen or a fluorine atom; R² and R⁹ are the same ordifferent and each represents a hydrogen atom, a halogen atom, a nitro,C₁₋₄ alkyl or cyano group; R³ and R⁸ are the same or different and eachrepresents a hydrogen, fluorine or chlorine atom, or a nitro, C₁₋₄alkyl, haloC₁₋₄ alkyl, haloC₁₋₄ alkoxy, haloC₂₋₄ alkenyl or (C₁₋₄alkoxy) carbonyl group provided that at least one of R³ and R⁸ is ahaloC₁₋₄ alkyl group; R⁴ and R⁷ are the same or different and eachrepresents a hydrogen or halogen atom or a C₁₋₄ alkyl group; R⁵represents a hydrogen atom, a halogen atom or a haloC₁₋₄ alkyl, C₁₋₄alkylthio or C₁₋₄ alkylsulphinyl group; and R⁶ represents a hydrogenatom or, when R⁵ is hydrogen, a methyl group.
 3. The compound accordingto claim 2, whereineach of X¹ and X² represents an oxygen atom; each ofR¹ and R¹⁰ represents a hydrogen atom; R² and R⁹ are the same ordifferent and each represents a hydrogen, fluorine or chlorine atom; R³and R⁸ are the same or different and each represents a trifluoromethylor pentafluoroethyl group; R⁵ represents a hydrogen or chlorine atom, ora methylthio group; and R⁶ represents a hydrogen atom.
 4. The compoundaccording to claim 3 selected from the group consisting of4-(4-chloro-α,α,α-trifluoro-m-tolyl)oxy!-6-(α,.alpha.,α,4-tetra-fluoro-m-tolyl)oxy!pyrimidine; 4,6-bis(4-chloro-α,α,α-trifluoro-m-tolyl)oxy!pyrimidine; 4,6-bis(α,α,α,4-tetrafluoro-m-tolyl)oxy!-2-chloropyrimidine; 4,6-bis(α,α,α,4-tetrafluoro-m-tolyl)oxy!-2-(methylthio)pyrimidine; 4-(α,α,α,4-tetrafluoro-m-tolyl)oxy!-6-(α,α,α-trifluoro-m-tolyl)oxy!pyrimidine; 4-(4-chloro-α,α,α-trifluoro-m-tolyl)oxy!-6-(α,.alpha.,α-trifluoro-m-tolyl)oxy!pyrimidine; 4,6-bis(α,α,α,4-tetrafluoro-m-tolyl)oxy!pyrimidine; and 4,6-bism-(1,1,2,2,2-pentafluoroethyl)phenoxy!pyrimidine.
 5. The compoundaccording to claim 4 wherein the compound is 4-(4-chloro-α,α,α-trifluoro-m-tolyl)oxy!-6-(α,.alpha.,α,4-tetra-fluoro-m-tolyl)oxy!pyrimidine.
 6. A method forcontrolling acarina and insects at a locus which method comprisesapplying to the locus an acaricidally or insecticidally effective amountof a compound having the structural formula ##STR10## wherein X¹, X²,R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ are as described in claim 1.7. The method according to claim 6 whereineach of X¹ and X² representsan oxygen atom, a sulphur atom or a group NH; R¹ and R¹⁰ are the sameand each represents a hydrogen or a fluorine atom; R² and R⁹ are thesame or different and each represents a hydrogen atom, a halogen atom, anitro, C₁₋₄ alkyl or cyano group; R³ and R⁸ are the same or differentand each represents a hydrogen, fluorine or chlorine atom, or a nitro,C₁₋₄ alkyl, haloC₁₋₄ alkyl, haloC₁₋₄ alkoxy, haloC₂₋₄ alkenyl or (C₁₋₄alkoxy) carbonyl group provided that at least one of R³ and R⁸ is ahaloC₁₋₄ alkyl group; R⁴ and R⁷ are the same or different and eachrepresents a hydrogen or halogen atom or a C₁₋₄ alkyl group; R⁵represents a hydrogen atom, a halogen atom or a haloC₁₋₄ alkyl, C₁₋₄alkylthio or C₁₋₄ alkylsulphinyl group; and R⁶ represents a hydrogenatom or, when R⁵ is hydrogen, a methyl group.
 8. The method according toclaim 7 whereineach of X¹ and X² represents an oxygen atom; each of R¹and R¹⁰ represents a hydrogen atom; R² and R⁹ are the same or differentand each represents a hydrogen, fluorine or chlorine atom; R³ and R⁸ arethe same or different and each represents a trifluoromethyl orpentafluoroethyl group; R⁵ represents a hydrogen or chlorine atom, or amethylthio group; and R⁶ represents a hydrogen atom.
 9. The methodaccording to claim 8 wherein the compound is selected from the groupconsisting of4- (4-chloro-α,α,α-trifluoro-m-tolyl)oxy!-6-(α,.alpha.,α,4-tetra-fluoro-m-tolyl)oxy!pyrimidine; 4,6-bis(4-chloro-α,α,α-trifluoro-m-tolyl)oxy!pyrimidine; 4,6-bis(α,α,α,4-tetrafluoro-m-tolyl)oxy!-2-chloropyrimidine; 4,6-bis(α,α,α,4-tetrafluoro-m-tolyl)oxy!-2-(methylthio)pyrimidine; 4-(α,α,α,4-tetrafluoro-m-tolyl)oxy!-6-(α,α,α-trifluoro-m-tolyl)oxy!pyrimidine; 4-(4-chloro-α,α,α-trifluoro-m-tolyl)oxy!-6-(α,.alpha.,α-trifluoro-m-tolyl)oxy!pyrimidine; 4,6-bis(α,α,α,4-tetrafluoro-m-tolyl)oxy!pyrimidine; and 4,6-bism-(1,1,2,2,2-pentafluoroethyl)phenoxy!pyrimidine.
 10. The methodaccording to claim 6 wherein the acarina are mites.
 11. A method forcontrolling animal ectoparasites which method comprises applying to theskin or coat of an animal an ectoparisiticidally effective amount of acompound having the structural formula ##STR11## wherein X¹, X², R¹, R²,R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ are as described in claim
 1. 12. Themethod according to claim 11 whereineach of X¹ and X² represents anoxygen atom, a sulphur atom or a group NH; R¹ and R¹⁰ are the same andeach represents a hydrogen or a fluorine atom; R² and R⁹ are the same ordifferent and each represents a hydrogen atom, a halogen atom, a nitro,C₁₋₄ alkyl or cyano group; R³ and R⁸ are the same or different and eachrepresents a hydrogen, fluorine or chlorine atom, or a nitro, C₁₋₄alkyl, haloC₁₋₄ alkyl, haloC₁₋₄ alkoxy, haloC₂₋₄ alkenyl or (C₁₋₄alkoxy) carbonyl group provided that at least one of R³ and R⁸ is ahaloC₁₋₄ alkyl group; R⁴ and R⁷ are the same or different and eachrepresents a hydrogen or halogen atom or a C₁₋₄ alkyl group; R⁵represents a hydrogen atom, a halogen atom or a haloC₁₋₄ alkyl, C₁₋₄alkylthio or C₁₋₄ alkylsulphinyl group; and R⁶ represents a hydrogenatom or, when R⁵ is hydrogen, a methyl group.
 13. The method accordingto claim 12 whereineach of X¹ and X² represents an oxygen atom; each ofR¹ and R¹⁰ represents a hydrogen atom; R² and R⁹ are the same ordifferent and each represents a hydrogen, fluorine or chlorine atom; R³and R⁸ are the same or different and each represents a trifluoromethylor pentafluoroethyl group; R⁵ represents a hydrogen or chlorine atom, ora methylthio group; and R⁶ represents a hydrogen atom.
 14. The methodaccording to claim 11 wherein the animal ectoparasites are ticks.
 15. Acomposition for controlling acarina, insects and animal ectoparasiteswhich composition comprises a carrier and an acaricidally,insecticidally or animal ectoparasiticidally effective amount of acompound having the structural formula ##STR12## wherein X¹, X², R¹, R²,R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ are as described in claim
 1. 16. Thecomposition according to claim 15 whereineach of X¹ and X² represents anoxygen atom, a sulphur atom or a group NH; R¹ and R¹⁰ are the same andeach represents a hydrogen or a fluorine atom; R² and R⁹ are the same ordifferent and each represents a hydrogen atom, a halogen atom, a nitro,C₁₋₄ alkyl or cyano group; R³ and R⁸ are the same or different and eachrepresents a hydrogen, fluorine or chlorine atom, or a nitro, C₁₋₄alkyl, haloC₁₋₄ alkyl, haloC₁₋₄ alkoxy, haloC₂₋₄ alkenyl or (C₁₋₄alkoxy) carbonyl group provided that at least one of R³ and R⁸ is ahaloC₁₋₄ alkyl group; R⁴ and R⁷ are the same or different and eachrepresents a hydrogen or halogen atom or a C₁₋₄ alkyl group; R⁵represents a hydrogen atom, a halogen atom or a haloC₁₋₄ alkyl, C₁₋₄alkylthio or C₁₋₄ alkylsulphinyl group; and R⁶ represents a hydrogenatom or, when R⁵ is hydrogen, a methyl group.
 17. The compositionaccording to claim 16 whereineach of X¹ and X² represents an oxygenatom; each of R¹ and R¹⁰ represents a hydrogen atom; R² and R⁹ are thesame or different and each represents a hydrogen, fluorine or chlorineatom; R³ and R⁸ are the same or different and each represents atrifluoromethyl or pentafluoroethyl group; R⁵ represents a hydrogen orchlorine atom, or a methylthio group; and R⁶ represents a hydrogen atom.18. The composition according to claim 17 wherein the compound isselected from the group consisting of4-(4-chloro-α,α,α-trifluoro-m-tolyl)oxy!-6-(α,.alpha.,α,4-tetra-fluoro-m-tolyl)oxy!pyrimidine; 4,6-bis(4-chloro-α,α,α-trifluoro-m-tolyl)oxy!pyrimidine; 4,6-bis(α,α,α,4-tetrafluoro-m-tolyl)oxy!-2-chloropyrimidine; 4,6-bis(α,α,α,4-tetrafluoro-m-tolyl)oxy!-2-(methylthio)pyrimidine; 4-(α,α,α,4-tetrafluoro-m-tolyl)oxy!-6-(α,α,α-trifluoro-m-tolyl)oxy!pyrimidine; 4-(4-chloro-α,α,α-trifluoro-m-tolyl)oxy!-6-(α,.alpha.,α-trifluoro-m-tolyl)oxy!pyrimidine; 4,6-bis(α,α,α,4-tetrafluoro-m-tolyl)oxy!pyrimidine; and 4,6-bism-(1,1,2,2,2-pentafluoroethyl)phenoxy!pyrimidine.
 19. A process for thepreparation of a compound having the structural formula I as claimed inclaim 1 in which R¹ =R¹⁰, R² =R⁹, R³ =R⁸ and R⁴ =R⁷, which processcomprises reacting under basic conditions a 4,6-dihalopyrimidinecompound having the structural formula ##STR13## in which R⁵ and R⁶ areas defined in claim 1 and each of Hal¹ and Hal², independently,represents a halogen atom, with a compound having the structural formula##STR14## in which X represents a group CH₂ Hal, COHal, OH, SH or NRH,Hal represents a halogen atom, and R, R¹, R², R³ and R⁴ are as definedin claim 1, in a molar ratio of at least 1:2.
 20. An intermediatecompound having the structural formula ##STR15## wherein R¹, R², R³, R⁴,R⁶, R⁷, R⁸, R⁹ and R¹⁰ are as described in claim 1; and R¹¹ representsan OH or NH₂ group, provided that at least one of R³ and R⁸ is ahaloC₁₋₆ alkyl group.